The below ground areas of buildings and other structures have traditionally been formed by excavating a hole using a temporary retaining system on the sides and then constructing the below ground walls of the structure in the excavated hole. The size of the excavation depends on the size of the building or structure that is being constructed and concrete is typically used to form the walls and floor. This method requires concrete forms to be constructed in the excavated hole and concrete to be poured into the forms. After the concrete hardens, the forms are removed and a floor is constructed on the foundation. For larger structures, it is usually necessary to construct footings or drive foundation pilings in the excavated area to support internal columns. These footings or piled foundations require the construction of additional forms and the pouring of more concrete.
The construction of the above ground area of the building or structure cannot begin until the construction of the foundation and the below ground area of the building or structure is completed. This means that the construction of the below ground area is on the critical path of a construction schedule and any delays in constructing the below ground area results in a delay in the completion of the building or structure. Accordingly, it is desirable to find a method of constructing the below ground area of a building or structure that does not require substantial completion of below ground construction before the above ground construction can begin. Such a method would allow above ground and below ground construction to be done simultaneously and decrease the construction time and cost.
When a conventional concrete foundation is poured using concrete forms, the excavation must extend beyond the perimeter of the foundation to allow room for constructing the forms. Similarly, in the past when sheet piling walls were constructed around the perimeter of an excavation, supports had to be installed on the exterior of the walls to anchor the walls in position so that the wall would not collapse inwardly when the interior side of the wall was excavated. Typically, these anchors extended out from the exterior of the sheet piling wall several feet or more. Consequently, the property owner had to either build further in from the property line to allow room for the installation of the anchors or receive permission from adjoining land owners to install the anchors on the adjoining property. Moreover, in many cases, existing structures prohibited this method of construction. Accordingly, neither alternative was completely satisfactory and there is a need for a construction method that allows the foundation wall to be built close to a property line. In addition, there is a need for a construction method using sheet piling sections that does not require supports or anchors to be installed on the exterior walls.
Many large constructions projects include buildings of different heights and complexity that have a longer construction schedule than other buildings. In order to minimize construction time, it is usually desirable to begin construction on these buildings as soon as possible, while the construction of other buildings does not have to be expedited. Under these circumstances, it may be desirable in some areas of the site to use a method of construction that does not require substantial completion of below ground construction before the above ground construction can begin and a more conventional construction method in other areas of the site. Such a method would be highly desirable since it would provide the benefits of both methods of construction.
In particular, there is a need for a simple and efficient solution to the construction of below grade structures that permits above ground construction to begin before the underground construction is completed. There is also a need for a method that reduces the overall time for construction and lowers the cost, while maximizing the available space underground. In addition, there is a need for a method of construction that expedites construction in selected areas of a site by simultaneously constructing above and below the ground.